1. Field of the Invention
The present invention relates to a multilayer wiring circuit board used for various electronic equipment and communication equipment. More particularly, the present invention relates to a multilayer wiring circuit board capable of reducing the characteristic impedance in a high frequency region. This invention also relate to a method of producing such a multilayer wiring circuit board.
2. Description of the Related Art
In order to remove noise, the frequency of which is in a band from 100 to 200 MHz, which is generated by an electric power source when switching is conducted on a circuit, it is conventional that a bypass condenser, which is arranged between the electric power source and the ground, is mounted on a circuit board so that the characteristic impedance can be reduced by increasing the capacitance of the circuit.
However, according to the above method by which the characteristic impedance is reduced by mounting the condenser on the circuit board so as to increase the capacitance, the number of the condensers to be mounted is increased when the circuit structure is made to be fine and the circuit density is increased to be high. Therefore, it is difficult to make the circuit structure fine so as to increase the circuit density by the above conventional method.
In order to solve the above problem, there is provided a method in which a condenser for removing high frequency noise, which is generated by the electric power source, is formed on the multilayer wiring circuit board.
For example, Japanese Unexamined Patent Publication No. 5-500136 discloses a multilayer wiring circuit board into which a condenser lamination body is incorporated so that an excellent capacitance characteristic can be obtained with respect to a plurality of parts which are operated at random.
Recently, there is a tendency that the switching frequency of the circuit is more increased. When the switching frequency of the circuit is increased more than a predetermined value, it becomes impossible to remove the high frequency noise even if the above conventional circuit structure is adopted.
This is related to the circuit inductance.